Visual Acuity (VA) tests in humans are usually performed by professionals such as ophthalmologists, optometrists and in some cases public-health nurses. Such tests require special training, special equipment and the patient's collaboration.
In a typical VA test the professional preforming the test presents visual stimulations such as presenting objects or characters (e.g. numbers and letters) at various sizes presented to the patient at decreasing size order. The patient is required to respond to the presented visual stimulation by identifying, verbally or in any other way (e.g., hand waving) the presented object or character. The professional tests each of the patient's eyes separately, while covering the other eye and the patient verbally required to notice the professional whether he/she sees the visual stimulation presented. A manual actuality test conducted by an optometrist that requires the patient's active participation takes more than 10 minutes and its accuracy relays heavily on the response of the patient and the professionalism of the optometrist.
Similar approach is implemented when testing a three-dimensional (3D) vision of the patient. The patient is given polarizing glasses and presented with a 3D visual stimulation. Here again the professional needs to hear the verbal response of the patient to various 3D visual stimulations in order to detect problems with the patient's 3D vision.
Tests that require a full verbal collaboration of the patient cannot be used to test or inspect infants, babies and people having difficulties in verbal communication such as people suffering from autism. The only known method of conducting VA tests in these groups is the use of Teller-Cards (also known as Teller Visual Acuity Cards). Teller cards are cards presenting vertical (or horizontal) black- and white strips at different widths and frequencies, starting at relatively wide stripes and ending with relatively narrow strips. Specially trained ophthalmologist tracts the eye movement of the patient using a small lamp as the patient is presented with the various Teller-cards. Each Teller card includes alternating black and white strips (either rows or columns) having a known/constant width alternating at a specific frequency. The Teller cards are presented to the patient in a contrast decreasing order starting with a card having wide strips and low frequency. When a patient cannot detect the contrast between the white and black strips (i.e., the card will look as a solid grey square), the professional conducting the test may notice a change in the concentration or gazing of the patient, indicating that the patient didn't notice the contrast presented. Teller cards are defined by a number of Cycles Per Centimeter (CPC) from the first strip to the last strip, presented at each cards. There are cards having 0.23, 0.32, 0.43, 0.64, 0.86, 1.3, 1.6, 2.4, 3.2, 4.8, 6.5, 9.8, 13.0, 19.0, 26.0 CPC, wherein, the 0.23 CPC has the widest strips and the 26.0 CPC has the narrowest strips. An eye of a patient having the ability to see the highest Teller card having 26.0 CPC has 6/6 vision (e.g., that at six meters test distance the patient could correctly identify a letter that a ‘normal’ sighted person should see at six meters, also referred to as normal vision). However, since the testing is done to both eyes simultaneously, the test can only give an indication that the patient may have a vision acuity problem. Some exemplary Teller-cards are illustrated in FIGS. 1A-1D.
Prior art methods for testing eyesight require the use of dilating eye drops that contain medication to enlarge (dilate) the pupil of the eye. There are two types of drops: one type stimulates contraction of the muscles that enlarge the pupil (such as phenylephrine); the other type relaxes the muscles that make the pupil constrict and also relaxes the muscle that focus the lens of the eye (such as cyclopentolate). The use of such dilating eye drops is very unpleasant and leaves the patient with blurred eyesight for couple of hours after the test.
Currently there is no reliable objective method or system for conducting acuity tests or diagnosing eyesight in general that does not relay on the patient's collaboration.